1. Field of the Invention
The present invention relates to an image forming apparatus. More particularly, the present invention relates to a waste-sludge discharging unit for removing waste sludge remaining on an image carrier of an image forming apparatus.
2. Description of the Related Art
Conventional image forming apparatuses use a developer to form an image. The image is formed by the developer after being transferred from an image carrier such as a photoconductive medium and a transfer belt. The image is formed on the image carrier. After being transferred to a printing medium, the developer typically remains on the image carrier. This is particularly true when a high-density liquid developer is used. Waste developer remains on the image carrier in the form of a sticky lump. The sticky lump is waste sludge comprising a gel clod and waste liquid. Accordingly, the image forming apparatus usually includes a waste-toner discharging unit for removing the waste developer or the waste sludge remaining on the image carrier.
FIG. 1 illustrates an example of a wet-type electrophotographic image forming apparatus which uses a high-density liquid developer and includes a conventional waste-sludge discharging unit.
Referring to FIG. 1, the wet-type electrophotographic image forming apparatus 1 comprises a plurality of photoconductive drums 10 on which an electrostatic latent image is formed by a laser beam emitted from a laser scanning unit (not shown) and developed by different colors of liquid developers T, respectively. A transfer belt 20 is provided on which the images formed on the plurality of photoconductive drums 10 are overlappingly transferred as a color image. A plurality of first transfer rollers 12 transfer the images formed on the photoconductive drums 10 onto the transfer belt 20 and a second transfer roller 30 transfers the color image formed on the transfer belt 20 onto a printing medium P which is supplied to the second transfer roller 30 by a paper feeding unit (not shown). The printing medium P having the color image thereon is transferred by the second transfer roller 30 and discharged after passing through a fixing unit (not shown) and a discharge roller (not shown). Thus, printing is complete.
The transfer belt 20 moves along a caterpillar track by a driving roller 22 and a driven roller 23. Adjacent to the driven roller 23, a cleaning blade 40 is equipped to remove the waste sludge S not transferred to the printing medium P but remaining on the transfer belt 20. A waste-sludge discharging unit 50 is formed on a lower part of the cleaning blade 40 to discharge the waste sludge S removed from the transfer belt 20 to waste-sludge storage 55.
The waste-sludge discharging unit 50 comprises a waste-sludge receiver 51 for receiving the waste sludge S removed from the transfer belt 20 by the cleaning blade 40. The waste-sludge discharging unit 50 also comprises an outlet 52 formed on a bottom of the waste-sludge receiver 51. The waste-sludge receiver 51 has a corresponding size to the cleaning blade 40. Thus, the waste sludge S being removed and gravitating from the cleaning blade 40 can be discharged through the outlet 52 without leaking to the outside of the waste-sludge receiver 51. The waste-sludge storage 55 for storing the discharged waste sludge S is disposed under the outlet 52 of the waste-sludge receiver 51. When filled with the waste sludge S, the waste-sludge storage 55 can be separated for emptying and remounted for reuse.
The process of removing the waste sludge in the image forming apparatus having the waste-sludge discharging unit 50 will now be described.
The electrostatic latent images are formed on the plurality of photoconductive drums 10, respectively, by laser beams emitted from the laser scanning unit in accordance with a printing command. The electrostatic latent images are developed into images of different colors, respectively, by liquid developers T supplied by a developing unit (not shown). The images formed on the plurality of photoconductive drums 10 are overlappingly transferred onto the transfer belt 20 by the respective first transfer rollers 12. Thus, a color image is formed. The color image formed on the transfer belt 20 is transferred onto the printing medium P by the second transfer roller 30. After transfer of the color image, typically portions of the liquid developers T are left on the transfer belt 20. The liquid developers T left is waste sludge S. The waste sludge S comprises a gel lump S1 of high viscosity and a waste liquid S2. While the transfer belt 20 moves along the caterpillar track by the driving and the driven rollers 22 and 23, the waste sludge S remaining thereon is removed therefrom by the cleaning blade 40. The waste sludge S streams along the cleaning blade 40. The waste sludge S streams along the cleaning blade 40 and is received into the waste-sludge receiver 51 and discharged to the waste-sludge storage 55 through the outlet 52 formed on the waste-sludge receiver 51.
In such a waste-sludge discharging unit 50, however, the waste sludge S that gravitates into the waste-sludge receiver 51 may accumulate at certain parts of the waste-sludge receiver 51. Due to the high viscosity of the waste sludge 5, the waste sludge S builds up instead of smoothly flowing out through the outlet 52. Once the waste sludge S starts accumulating on the bottom of the waste-sludge receiver 51, the outlet 52 may clog due to the waste sludge S removed by the cleaning blade 40. The waste sludge S will continue to accumulate in the waste-sludge receiver 51. As a consequence, deterioration of the image and leakage of the developer may result. Thus, replacement of an image cartridge, which includes the transfer belt 20, may be required. In other words, the accumulation of waste sludge S in the conventional waste-sludge discharging unit 50 reduces the lifespan of the image cartridge.
Accordingly, there is a need for a waste-sludge discharging unit for discharging waste sludge removed from an image carrier such as a transfer belt that prevents accumulation of the waste sludge in a waste-sludge receiver and increases the longevity of the image cartridge.